In drilling wells for oil and gas exploration, understanding the structure and properties of the associated geological formation provides information to aid such exploration. In recent years, optical sensing methods have become quite popular in acquiring such information. Even after the well is drilled, methods based on optical sensing can be used downhole to measure properties of the geological formation, as well as composition of fluid in and in the vicinity of the well bore, for example oil and water. Light can be guided down the wellbore via optical fibers.
Interferometric methods can be used to determine, for example, the composition of fluids down hole. However, these techniques can be limited due to many factors that can degrade the signal-to-noise ratio (SNR) of the received signal. For example, there may be limits on depth that the technique can operate effectively due to a signal loss in optical fibers, limits on signal strength due to an upper limit to which the strength of the signal can be increased without increasing the noise, or limits on the frequency/spatial resolution.